1. Field of the Invention
This invention relates generally to a thermal printing apparatus and more particularly to a thermal printing apparatus in which a slave tape and a master tape run at the same speed, the running slave tape is heated by a heating means, for instance, a halogen lamp or a heat shoe, and then signals recorded on the master tape are thermally recorded on the slave tape when both of the tapes are pressed to each other by a printing roller.
2. Description of the Prior Art 125.degree.
As generally known, the slave tape should be heated up to a temperature over the Curie point (125 to 130.degree.C), in the thermal printing apparatus.
In the conventional thermal printing apparatus, the slave tape begins to be heated with the closing of the tape start switch, by the heating means. However, the rise time of the tape running speed is very short in which the tape running speed reaches the predetermined speed after the beginning of the tape running. On the other hand, the rise time of the tape temperature is relatively long in which the slave tape is heated up to the predetermined temperature after the beginning of the tape heating. While the slave tape is not heated up to the predetermined temperature, the slave runs uselessly. That is a serious problem when the tape running is stopped for any reason during the thermal printing operation.
The heating means such as a halogen lamp cannot be exposed directly to a cooling air for rapid cooling, since the halogen lamp is easily damaged by the cooling air. Therefore, the halogen lamp has heretofore been cooled by spontaneous radiation after the cut-off of the power supply to the halogen lamp. However, the halogen lamp is not sufficiently cooled without the lapse of a long time.
When the tape is threaded on with the exchange of a slave tape, there are the dangers that the tape contacts unexpectedly with the halogen lamp to be damaged thereby and that the operator's hand gets burned in contact with the halogen lamp. Unless the halogen lamp is sufficiently cooled, such dangers cannot be avoided. Accordingly, it takes a great deal of time to exchange the tape. Operation efficiency is very low.
When the tape is stopped during the thermal printing operation, the tape is apt to be heated excessively and to be damaged. It is difficult to freely stop the tape running during the thermal printing operation.